Description: Pesticides constitute a group of chemical substances that are used for the control of unwanted organisms. Inorganic arsenicals (arsenic) and atrazine represent two examples of pesticides that have been applied in agricultural areas of Mississippi to promote crop protection. The available toxicological data on these two chemicals indicate that a number of significant works have already been done to assess their toxic effects on humans and laboratory animals. However, it is stated that limited information is published on their genotoxic effects and their toxicokinetics. Also, little data are available on their combined toxicity to humans and experimental animals. This research is proposed to assess the toxicokinetics, histopathology, and in vivo genotoxic effects of arsenic and atrazine, using fish and rats as model test animals. The specific aims of this research are: 1) to determine the acute toxicity of arsenic, atrazine, and arsenic-atrazine mixture in fish and rats; 2) to evaluate the toxicokinetics of arsenic and atrazine in fish and rats; 3) to conduct biochemical analyses to determine the effects of arsenic and atrazine on the activities of specific indicator enzymes; 4) to determine the genotoxic effects of arsenic and atrazine, by assessing the type and extent of chromosome aberrations, the mitotic index, and the DNA damage in rats; 5) to utilize the Microtox and the Mutatox Test Systems to determine the relative toxicities and the genotoxic potential of arsenic and atrazine; and 6) to conduct histopathological examinations to monitor the extent of tissue injury following chronic exposure of fish and rats to arsenic and atrazine. All acute and chronic bioassays will be conducted following previously described/published test-protocol experiments that will be designed around the themes of toxicokinetics, acute, chronic and genotoxicity of arsenic and atrazine.